Explain BAC as long sequence clonning vector.

Solution 

Bacterial Artificial Chromosomes (BACs) are DNA constructs that are circular in shape and are used for transformation and cloning in bacterial cells like Escherichia coli. 

Segments of an organism's DNA, ranging from 100,000 to about 300,000 base pairs, can be inserted into BACs. The BACs, with their inserted DNA, are then taken up by bacterial cells. As the bacterial cells grow and divide, they amplify the BAC DNA, which can then be isolated and used in sequencing DNA.

The gene components in a BAC vector are -
rep6 for plasmid regulation,
a selectable marker for antibiotic resistance,
parA and parB for F-plasmid DNA,
and T7 and Sp6 for transcription of inserted genes.